Why are coarse-grained force fields too fast? A look at dynamics of four coarse-grained polymers

Coarse-grained models decrease the number of force sites and thus reduce computational requirements for molecular simulation. While these models are successful in describing structural properties, dynamic evolution is faster than the corresponding atomistic simulations or experiments. We consider coarse-grained models for four polymers and one polymer mixture, where accurate dynamics are obtained by scaling to match the mean-squared displacements of the corresponding atomistic descriptions. We show that the required scaling is dictated by local friction and that this scaling is only valid after the onset of continuous motion.